Natural gas hydrate is a potential resource to meet the ever-increasing energy demand. Yet wellbore/pipeline blockage due to hydrate regeneration poses serious safety hazards during gas hydrate production. In order to estimate and effectively manage the blockage risk, we studied the hydrate regeneration behavior in wellbore during hydrate production. A method is developed to predict where gas hydrates regenerate (i.e. the hydrate regeneration region, HRGR) in the wellbore. The HRGRs with different production methods were studied. The results indicate that hydrates regenerate in wellbore. The hydrates can deposit onto the wall of the production tubing and form a growing solid layer, which narrows the tubing and even reults in complete blockage. The simulation work indicates that there tends to be a rather large HRGR in the production tubing regardless what production methods are adopted. The blockage risk is usually much higher in the region where a higher subcooling is encountered. This region is the high blockage risk region (HBRR). For the depressurization method, the HRGR shrinks as the depressurization amplitude increases. Accordingly, the HBRR and most vulnerable site become shallower. Therefore, the blockage risk is reduced. Similar trend is found as the thermal/chemical injection methods are used. However, for thermal injection and chemical injection, there are no significant change in the HBRRs and the most vulnerable sites. Only an unnoticeable slight upward trend is found for the thermal injection cases.

You can access this article if you purchase or spend a download.